The following description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art to the presently claimed invention, nor that any of the publications specifically or implicitly referenced are prior art to that invention.
The exendins are peptides that are found in the venom of the Gila-monster, a lizard common in Arizona and Northern Mexico. Exendin-3 (SEQ ID NO:1) is present in the venom of Heloderma horridum, and exendin-4 (SEQ ID NO:2) is present in the venom of Heloderma suspectum (Eng et al, J Biol Chem, 265:20259-62, 1990; Eng et al., J Biol Chem, 267:7402-05, 1992). The amino acid sequence of exendin-3 is shown in FIG. 2. The amino acid sequence of exendin-4 is shown in FIG. 3. The exendins have some sequence similarity to several members of the glucagon-like peptide family, with the highest homology, 53%, being to GLP-1(7 36)NH2 (SEQ ID NO:3) (Goke et al, J Biol Chem, 268:19650-55, 1993). GLP-1(7 36)NH2, also known as proglucagon(78-107) or simply, “GLP-1,” has an insulinotropic effect, stimulating insulin secretion from pancreatic β-cells. The amino acid sequence of GLP-1 is shown in FIG. 4. GLP-1 also inhibits glucagon secretion from pancreatic α-cells (Orsov et al, Diabetes, 42:658-61, 1993; D'Alessio et al, J Clin Invest, 97:133-38, 1996). GLP-1 is reported to inhibit gastric emptying (Willms et al, J Clin Endocrinol Metab 81(1): 327-32, 1996; Wettergren et al, Dig Dis Sci 38 (4):665-73, 1993), and gastric acid secretion. Schjoldager et al, Dig Dis Sci 34(5):703-8, 1989; O'Halloran et al, J Endocrinol 126(1):169-73, 1990; Wettergren et al, Dig Dis Sci 38(4):665-73, 1993). GLP-1(7 37), which has an additional glycine residue at its carboxy terminus, also stimulates insulin secretion in humans et al., Diabetes, 42:658-61, 1993). A transmembrane G-protein adenylate-cyclase-coupled receptor believed to be responsible for the insulinotropic effect of GLP-1 has been cloned from a line (Thorens, Proc. Natl. Acad. Sci. USA 89:8641-45 (1992)).
Exendin-4 reportedly acts at GLP-1 receptors on insulin-secreting cells, at dispersed acinar cells from guinea μg pancreas, and at parietal cells from stomach; the peptide is also said to stimulate somatostatin release and inhibit gastrin release in isolated stomachs (Goke, et al., Them. 268:19650-55, 1993; Schepp, et al., Eur. J. Pharmacol., 1994). Exendin-3 and exendin-4 were reportedly found to stimulate cAMP production in, and amylase release from, pancreatic acinar cells (Malhotra, R., et al., Regulators 1992; Raufman, et al., 267:21432-37, 1992; Singh, et al., 53:47-59, 1994). Based on their insulinotropic activities, the use of exendin-3 and exendin-4 for the treatment of diabetes mellitus and the prevention of hyperglycemia has been proposed (Eng, U.S. Pat. No. 5,424,286).
Agents which serve to delay gastric emptying have found a place in medicine as diagnostic aids in gastro-intestinal radiologic examinations. For example, glucagon is a polypeptide hormone which is produced by the a cells of the pancreatic islets of Langerhans. It is a hyperglycemic agent which mobilizes glucose by activating hepatic glycogenolysis.
It can to a lesser extent stimulate the secretion of pancreatic insulin. Glucagon is used in the treatment of insulin-induced hypoglycemia, for example, when administration of glucose intravenously is not possible.
However, as glucagon reduces the motility of the gastro-intestinal tract it is also used as a diagnostic aid in gastro-intestinal radiological examinations. Glucagon has also been used in several studies to treat various painful gastro-intestinal disorders associated with spasm. Daniel, et al. Med. J., 3:720, 1974) reported quicker symptomatic relief of acute diverticulitis in patients treated with glucagon compared with those who had been treated with analgesics or antispasmodics. A review by Glauser, et al., (J. Am. Coll. Emergency Physns, 8:228, 1979) described relief of acute esophageal food obstruction following glucagon therapy. In another study glucagon significantly relieved pain and tenderness in 21 patients with biliary tract disease compared with 22 patients treated with placebo (M. J. Stower, et al., J. Surg., 69:591-2, 1982).
Methods for regulating gastrointestinal motility using amylin agonists are described in International Application No. PCT/US94/10225, published Mar. 16, 1995. Methods for regulating gastrointestinal motility using exendin agonists are described in a U.S. Pat. No. 6,858,576. Certain exendin agonists are described in U.S. Pat. Nos. 7,223,725 and 7,220,721.